Electric-motor control.



H. 1). JAMES.

ELECTRIC MOTOR CONTROL.

APPLICATION FILED NARA, 1907.

Patefited Nov. 1,1910.

2 SHEETS-SHEET 1.

ATTORNEY ru z mums PETERS 60., WASHINGTON, u. c

INVENTOR n. D.- JAMES.- ELECTRIC MOTOR CONTROL.- grumgno'n rum) IAIA,1907.

974,152. -P nted Nov .'1, 1910. I Mums-93mm.

WITNESSES 5 INVENTOR 'm: NORRIS PETERS cm, vusnmamw, 114 C4 ATTORNEYUNITED STATES PATENT OFFICE.

HENRY 1). JAMES, 015 PITTSBURG, PENNSYLVANIA, ASSIGNOR T WESTINGHOUSEELECTRIC 8:; MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC-MOTOR CONTROL.

Application filed March 4, 1907.

To all whom it may concern:

Be it known that I, HENRY D. JAMES, a citizen of the United States, anda resident of Pittsburg, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Electric-Motor Control, of which the following is a specification.

My invention relates to control systems for electric motors, and hasspecial reference to systems of this character which severally comprisea plurality of independently operated accelerating and control switches.

The object of my invention is to provide, in a system of the aforesaidclass, means for maintaining the majority of the accelerating switchesin open position, except for a short starting period, so that thestarting resistance may be re-inserted when it is desired to bring themotor to rest.

Shunt or compound wound electric motors are often employed for variablespeed service in connection with elevators and machine tools and, inorder to avoid flashing over and other abnormal and detrimentalconditions when a motor of this character is retarded from high speedoperation under weak field conditions, I automatically reinsert theresistance which was cut out as the motor accele *ated.

Figure 1 of the accompanying drawings is a diagrammatic view of a systemof electric motor control arranged in accordance with my invention. Fig.2 is a view, similar to Fig. 1, of a simplified system having a slightlymodified arrangement of accelerating switches.

Referring to Fig. 1 of the drawings, electrical energy may be suppliedfrom any convenient source, through supply conductors 1 and 2, to anelectric motor 3 having a .shunt field magnet winding at and seriesfield magnet windings 5 and 6. The circuit connections for the motor aregoverned by electrically operated reversing switches 7, 8, 9 and 10, aline switch 11, accelerating switches 12, 13 and 141 and a controlswitch 15 all of which are governed by a master switch 16 and a limitswitch 17. The switch 16 is adapted to occupy either of two forwardpositions a and 7) and either of two Specification of Letters Patent.

Patented Nov. 1, 1910.

Serial No. 360,512.

I reverse positions a and b and the switch 17 may occupy either ofpositions a: and y in which a rotation of motion in one direction ispermitted, and either of positions ac and 1 in which a rotation of themotor is permitted only in the reverse direction.

During the normal operation of the motor the limit switch 17 occupies amid-position K and, under these conditions, the motor may be stopped bymoving the master switch 16 to its mid-position H. Assuming that thelimit switch 17 occupies the position K and that the master switch 16 ismoved to posi tion a from position H, the circuit connections are asfollows: Energy is supplied from line conductor 1 through a controlconductor 18, stationary contact member 19 of the master switch 16 andmovable contact arm 20, to the stationary contact members 21 and 22. Onebranch of the circuit is continued through contact member 21, conductor23 and actuating magnet winding 24: of line switch 11 to the oppositeline conductor 2. The other branch of the circuit is fro line conductor1 to stationary contact me nber 22 of switch 16, through conductor 52*.stationarv contact members 26 and 27 of 5 the switch 17 (which arebridged by a movable contact member 28), conductor 29, masnet winding 30of reversing switch 9, conductor 31, stationary contact fingers 82 ofthe reversing switch 7 (which are bridged by contact member 33),conductor 34-, cantact fingers 35 (which are bridged by a movablecontact member 36 of the reversing switch 10), conductor 37, contactfingers 88 (which are bridged by movable contact member 39 of the lineswitch 11 that is closed by reason of the energizing of its magnetwinding 2st) to the opposite line conductor 2. The switches 11 and 9 areclosed in the order named as soon as the circuits above traced arecomplete and energy is supplied from line conductor 1 through thereversing switch 9, conductor 10 and conductor 11, to the magnet windinga2 of the reversing switch 8, from which point circuit is completed asalready described through conductor 34. The energizing of the magnetwinding 4-2 effects the closure of the switch 8 so that a main circuitis completed from line conductor l through switch 9, conductors 40 and13, the armature of motor 3, conductors 411 and 4:5, switch 8, conductor4:6, series field magnet windings 5 and (3, a resistance 17 and theswitch 11 to the opposite line conductor 2. The motor is thus startedunder strong field conditions and with a suitable resistance inserted inits armature circuit.

If the master switch is moved from the position a to the position b, the.motor will be accelerated automatically, a circuit being completed fromthe conductor 18, through stationary contact members 19 and 48 of themaster switch, conductor 19, stationary contact members 50 (which arebridged by movable contact member 51 of switch 17), conductor 52,contact fingers 53 (which are bridged by contact member when the controlswitch 15 is open), conductor 55, contact fingers 56 (which are bridgedby contact member 57 when the line switch 11 is closed), magnet winding58 of accelerating switch 12 and resistance 17 to the opposite lineconductor 2. is soon asthe switch 12 is closed, the aforesaid circuit iscompleted from conductor through contact fingers 59 (which are bridgedby contact members 60), magnet winding 61 of the accelerating switch 18,series field magnet (S and switches 12 and 11 to the opposite lineconductor. In a similar manner, the switches 13, let and 15 are closedsuccessively. As the accelerating switches 12. 13 and 1 1 are closed,resistance 47 and series field magnet windings G and 5 are successivelyshort-circuited. The closure of the control switch 15 connects theconductor #16 to the line conductor 2. through switches 11 and 15 andinterrupts the circuit which was completed through contact fingers andbridging contact member 54. This interruption de'e'nergizes the magnetwinding 58 and permits the switch 12 to open after which the switches 13and 1 1 successively open, since the circuit through each magnet windingis dependent upon the closure of the adjacent switch.

It will be readily understood that. a considerable time will elapsebetween the closure of the control switch 15 and the opening of theswitch 14-. so that ample time is allowed for the establishment of acircuit from conductor through contact fingers G2 (which are bridged bycontact member 63 when the switch 15 is closed), actuating magnetwinding 6-t and switches 15 and 11 to the line conductor 2.

The shunt field 4 is connected in a circuit (established when the switch8 is closed), from conductor 41, through contact fingers 65, conductor66 in the neld magnet, conductor 67 conductor 68, contact fingers G9(which are bridged by the contact member 63 when the control switch 15is open), conductor 7t) and line switch 11 to line conduct-or and afterthe motor is accelerated as far as possible, by reason of the armatureresistance 17, the series field magnet windings 5 and 6 beingshort-circuited, its speed is still more increased when switch 15 isclosed by reason of the fact that the circuit through contact fingers 69is interrupted and a resistance 71, which was formerly short-circuited,is now connected in series with the field magnet winding.

Since, in the acceleration of the motor, the

control switch 15 was closed last, when the master switch is moved fromthe position I) to the position a and the motor is retarded, this switchwill open first, but if the field of the motor is suddenly strengthenedwhen the motor is operating at a high speed, the counter elect-romotiveforce of the armature may considerably exceed the impressedelectromotive force of the line. A voltage disturbance on the line willresult in this event and, furthermore, the motor is liable to tlash overor destructive electric arcs may at least be formed at the connnutatorbrushes. This ditliculty is avoided in the arrangement illustrated,since the accelerating switches 12, 13 and 14- are opened, ashereinbefore explained, as soon as the control switch .15 is closed,consequently, when the switch 15 is open and the field is strengthened,the accelerating resistance 4t? is included in the armature circuit andelcctromotive force disturbances in the supply circuit aresubstai'itially avoided. If the master switch is now moved from theposition a to its oil position the line switch 11 will be opened, thecircuit through its magnet winding being interrupted, and a magnetwinding 72 of a switch 73 will be connected across the armature of themotor through conductor 74, contact fingers 75 (which are bridged by acontact member 57 of the switch 11), and conductor 76. The switch 73 isheld closed until the counter electromotive force of the motor bc comesnegligible and, therefore, the current generated in the motor armatureis absorbed in a resistance 77 during this final period of retardation.If the master switch is moved successively into positions a and 7) themo tor will be accelerated in av similar manner except that switches Tand 10, instead of switches S and 9, will be closed and the di rectionin which the current flows through the armature of the motor will bereversed. Substantially the same conditions are brought about when thelimit switch 17 is moved successively to positions a: and :I/ or topositions 00 and 1/ as are obtained when the master switch is moved fromits position b or Z) to position H through positions (I, or a exceptthat the limit switch is so arranged as to be automatically actuated bythe car or other device operated by the motor at the ends of its traveland to prohibit Cir a further movement of the motor in. the l forclosing the control switch, of means, de-

same direction.

In addition to the regenerative braking ell'ect obtained when theresistance 77 is included in. the armature circuit of the motor, amechanically applied brake 78 (it well known. form may be employed, arelease magnet winding 78 being provided, as indicated in Fig. 1. Thismagnet winding will be energized as soon as either of the reversingswitches S) or is closed and, conscquently, the brake which it maycontrol will be released just before the motor is sta rted.

Referring to Fig. 2, switches 79, 80, Si and correspond to switches 11,12, 14: and 15 in Fig. 1 and are adapted to etl'ect the .cceleration ota compound wound motor 88 (having a series field magnet winding '84s anda shunt field magnet winding ,by gradir ally short-circuiting aresistance 86 and finally bridging the intermediate switches 80 and 81as the switches l2, l3 and 14 are bridged in the system shown. in Fig.l. \Vhen the switch 82 is closed, energy is sup plied to its magnetwinding through an auxiliary resistance 87 and, consequently,

the current required for the control circuits during the full speedoperation of the motor less than that required for the circuits duringits acceleration.

I claim as my invention:

1, In a control system for electric motors, the combination with aseries of independently operatet switches, actuating magnet windings foreach switch, and means for so energizing the windings as to close theswitches in a predetermined order, of means for causing the switches toautomatically open in the order in which they were closed.

:2. In a system of electric motor control, the combination with a seriesof electrically governed switches that are adapted to close in apredetermined sequence, and independent means for operating each switch,of means for automatically opening the switches in the same sequence.

3. In a system of electric motor control, the combination with aplurality of electrically governed accelerating switches, a controlswitch that bridges the accelerating switches, and means for closing theswitches in a predetermin d order, of means, dependent upon the closureof the control switch, for automatically opening the remaining switchesin the order in which they were closed.

4-. In a control system, the combination with a motor having armatureand field magnet windings, automatic accelerating switches therefor, acontrol switch adapted to bridge the accelerating switches, means forclosing the accelerating switches in a predetermined order, and means,dependent upon the closure of the accelerating switches,

'pendent upon the closure oi? the control switch, for automaticallyopening the accelerating switches in the order in which they wereclosed.

5. In a system of control, the combination with an electric motor, anaccelerating resistance therefor, a field magnet, a resistance therefor,a series of independently operated switches for cutting outtheaccelerating resistance, a control switch for bridging the acceleratingswitches and for inserting the field resistance, of means, dependentupon the closure of the control switch, for automatically opening theaccelerating switches in a predetermined order.

(3. In a system of control, the combination with an electric motor, anaccelerating resistance therefor, a field magnet, a resistance therefor,a series of independently operated switches that are adapted to close ina pre determined sequence and to cut out the accelerating resistance, acontrol switch tor bridging the accelerating switches and for insertingthe field resistance, of means, de pendent upon the closure of thecontrol switch, for automatically opening the accelerating switches inthe order in which they are closed.

'7. In a system of electric motor control, the combination with anarmature resistance,

' a field resistance and inde )endently operating switches forautomatically supplying energy to the motor through said armatureresistance, gradually short-circuiting said armature resistance andfinally weakening the motor field by inserting said field resistance, ofmeans to; automatically bringing the motor to rest by simultaneouslyeliminating the field resistance and re-inserting the armatureresistance before the supply of energy is interrupted.

8. In a. control system, the combination with a supply circuit, anelectric motor having an armature, a shunt field magnet wind ing andseries field magnet windings, a shunt field resistance and an armatureresistance, of a plurality of independently operated switches forsuccessively and automatically shortcircuiting the field resistance,connecting the motor to a supply circuit with the series field magnetwinding and the armature resistance connected in series with the motorarmature, gradually reducing the armature, resistance, short-circuitingthe series field magnet windings and reinscrting the shunt fieldresistance, and means for automatically stopping the motor bysimultaneously short-circuiting the field resistance, reinserting theseries field magnet windings and the ari'nature resistance and finallyinterrupting the supply circuit.

9. In a system of electric motor control, the combination with aplurality of governing switches, of means for automatically closing theswitches in a predetermined sequence, and means dependent upon theclosure of the last switch, for opening the other switches in apredetermined order.

10. In a. system of electric motor control, the combination with aplurality of accelerating switches, and a control switch, of meansdependent upon the closure of the control switch, for automaticallyopening the 1 other switches in the order in which they 10 were closed.

In testimony whereof I have hereunto subscribed my name this 28th day ofFebruary, 1907.

HENRY D. JAMES. lVitnesses VILLIAM A. PARIS, BIRNEY HINES.

